Based on Nebel and Wright, Environmental Science 8th
Ed, @2000
1.Natural
communities are organized into units we call ecosystems.What are ecosystems?How
are they
organized into
larger units?
“(A)n ecosystem is a
grouping of plants,animals,and microbes occupying an explicit unit of space and
interacting with each other and with their environment.” “Similar or related
ecosystems or landscapes are often grouped together to form major kinds of
ecosystems call biomes.” “(A)biome is still basically a certain biotic
community supported and limited by certain abiotic environmental factors.”
2.The organisms
in every ecosystem can be assigned to trophic categories.What are the
categories?How do they function together in food webs to make sustainable
system?
There are 3 major
categories of organisms.These categories are producers,consumers and detritus
feeders and decomposers.“Together these groups produce food,pass it along food
chains,and return the starting materials to the abiotic parts of the
environment.” “(A)ll food chains,food webs,and trophic levels must start with
producers,and producers must have suitable environmental conditions to support
their growth. Populations of all heterotrophs,including humans,are ultimately
limited by what plants produce, in accordance with the concept of the biomass
pyramid. Should any factor cause the productive capacity of green plants to be
diminished, all other
organisms at higher trophic levels will be diminished accordingly.”
3.Many
non-trophic relationships also exist in ecosystems. What role do mutualism and
competition play in ecosystems?
Mutualism is a
non-feeding relationship between species where both benefit. Mutualistic
relationships result in survival advantages for the species involve and may
result in a species to being able to survive in an environment that is
otherwise in hospitable,e.g.,alga in association with fungus to form lichen.
Competition between
species is reduced by each species being adapted to its own habitat and/or
niche. The more habitats and niches existing within an ecosystem the more
species can be accommodated; this is how diversity is possible and why complex
ecosystems are considered essential.
4.Environmental
factors can be categorized into conditions and resources. How do these factors act as limiting factors
in the distribution of different species in ecosystems?
“Conditions are abiotic
factors that vary in space and time but are not used up or made unavailable to
other
species.” Temperature,,
a condition will limit where a species exists because there are temperatures
above or below which organisms die (or cannot reproduce).“Resources are any
factors – biotic or abiotic – that are consumed by organisms.” Like
conditions,,if resources are found in excessive or limited quantities,the
survival
of organisms will not be
optimal.
5.Precipitation
and temperature are the predominant determinants of climate.How do these
factors interact to produce the different biomes around the globe?
“Different temperature
and rainfall conditions may occur in almost any combination to give a wide
variety of climates.In turn,a given climate will support only those species
that find the temperature and precipitation
levels optimal or at
least within the range of tolerance.” Climate creates distinct conditions that
result indifferent biomes.
6.Revolutionary
changes have in human culture have greatly changed the relationship between
humans and the environment.How have the Neolithic and Industrial Revolution
impacted the natural environment,and what is meant by the Environmental
Revolution.
The development of
agriculture,resulting in a more abundant and reliable food supply,is called the
Neolithic Revolution.A more reliable and abundant food supply resulted in the
growth of the human population. Greater incentives and more potential for the
development of technology were a result of theNeolithic Revolution. Resource
use increased. The primary differences between the Industrial Age and the Neolithic Age are the
energy sources used and the scale of resources use.The Neolithic Age relied on
animal and renewable energy sources (trees,dung,etc.) while the Industrial Age
was energized by fossil fuels.The Neolithic Age used fewer resources than the
Industrial
Age.
Chapter
Three
1.All the elements that comprise living things come from the environment.What are these key elements?Where is each found?
Nitrogen,carbon,oxygen,hydrogen,phosphorus,and
sulfur are the key elements in nature.Each is found in all living things and
detritus.Carbon is found as carbon dioxide in the atmosphere.Oxygen and
nitrogen are found in the atmosphere.Hydrogen is found in water,and the
atmosphere.Phosphorus and sulfur are found in soil and rock.
2.All chemical
reactions taking place in living things involve energy.What are the different
forms of energy,and what are the laws that govern energy exchange?
The different forms of
energy are potential (energy in storage),kinetic (energy in motion),and
chemical (the potential energy found in gasoline and other fuels)energy.The
First and Second Laws of Thermodynamics are the laws that govern energy
exchange.
3.Photosynthesis
and cell respiration are the two fundamental biological processes. What matter
and energy
changes occur in
these two processes? Relate them to the dynamics of ecosystems.
In photosynthesis the
matter change is the combination of carbon dioxide and water to form
glucose,and oxygen.The energy change during photosynthesis is carbon dioxide
and water,which have low potential energy,being changed to glucose,which has
high potential energy,and oxygen through the capture of light energy from the
sun.
In cell respiration the
matter change is the burning of glucose using oxygen to produce carbon dioxide
and water.The energy change during cell respiration is the burning of a high
potential energy substance,glucose,to form low potential energy
substances,water and carbon dioxide. Producers combine inorganic,low-potential
energy matter using the sun ’s energy to form high potential energy matter that
they and consumers use as fuel for growth,reproduction,etc.Matter and energy
begin their movement through the ecosystem with photosynthesis.Cell respiration
releases matter for use in building the
molecules contained in
an organism.Additionally,cell respiration releases matter back to the
environment for use in photosynthesis.“Sixty to ninety percent of the food that
consumers eat,digest and absorb is oxidized for energy.” Ten to forty percent
of the food that consumers eat is converted to body tissue..
4.Detritivores
and decomposers promote the breakdown of organic matter.What are they,and how
important is their role?
Detritivores consume
fecal wastes,and dead plants and animals;they are consumers,whereas,
decomposers are primary detritivores.Without detritivores and decomposers the
matter in detritus would never be released to be re-absorbed by plants.The
energy remaining in the detritus would remain.The food web
would stop without the
cycling of nutrients from detritus through the detritivores.
5.The flow of
energy is one of the vital processes that occur in all ecosystems.Describe how
energy flows in terms of trophic levels.How efficient are the transfers of
energy?
Energy flows from the
sun,through producers,to consumers.Producers through the process of photosynthesis
absorb energy from the sun.Producers absorb only 2%of the energy from the
sun.Energy flows from producers to herbivores to carnivores.On average 10%of
the energy found at any trophic level is transferred to the next trophic
level.At each trophic level most organisms are not consumed,most of the
consumed matter is used as energy,and some of the consumed matter is passes
through the organism undigested.At each level,energy is released to the
environment in the conversion of high potential energy to low potential energy.
6.The recycling
of elements is another vital functional process occurring in all
ecosystems.Describe the biogeochemical cycles for carbon,phosphorus and
nitrogen.How have humans impacted these three cycles?
Carbon cycle:The carbon cycle ‘begins
’ with the two reservoirs::carbon dioxide in the atmosphere and bicarbonate
molecules in water.Carbon atoms from carbon dioxide are incorporated into
producers through the process of photosynthesis.The carbon in producers is
transferred to consumers via the food web.Carbon is released back to the
atmosphere through decomposition by decomposers and detritus
feeders.Respiration
releases carbon as
carbon dioxide for land-based organisms and as inorganic carbonate in aquatic
ecosystems. Non-trophic transfers of carbon include the geological
sedimentation of carbon,thereby removing carbon from solution,and the
combustion of fossil fuel carbon,thereby releasing carbon to the atmosphere.The
main impact humans have on the carbon cycle is through the burning of fossil
fuels and deforestation resulting in
increased levels of
carbon dioxide in the atmosphere.
Phosphorus cycle:The phosphorus cycle
‘begins ’ with its reservoirs::phosphorus in rock and soil minerals. When rocks
break down,phosphate and other phosphorus ions are released to soil or
water.Plants absorb phosphate from soil or water and incorporate it into the
plant ’s structure.The food web transfers phosphorus from producers to
herbivores to carnivores.Cell respiration (and decomposition)result in the
release of
phosphorus ions (in
urine or other waste products)to the environment for re-uptake by
plants.Phosphorus does not have a gas phase;it is recycled only if the wastes
containing it are deposited back to the soil “from which it came ”.Humans disrupt the
phosphorus cycle by removing matter from ecosystems such that phosphorus is not
returned to the ecosystem from which it came.An example is the removal of trees
from tropical rain forests where the recycling of nutrients is nearly
100%efficient and there are few to no reserves of nutrients in the soil.
Another way in which humans disrupt the phosphorus cycle is through the
addition of chemical fertilizer to lawns and farmland.Much of the phosphorus
fertilizer runs off the land and is added to aquatic ecosystems where
phosphorus is naturally found in small quantities.(Phosphorus is a limiting
factor in aquatic ecosystems.)
Nitrogen cycle:The nitrogen cycle
‘begins ’ with its reservoir::nitrogen dioxide in the atmosphere.Nitrogengas is
‘fixed ’ by bacteria into nitrate compounds or may be ‘fixed ’ by
lightening..Nitrate compounds are takenup by producers and incorporated into
essential organic compounds.Nitrogen is moved through the food web by
herbivores consuming producers and carnivores consuming herbivores.Nitrogen is
released back to the soil,primarily as ammonium compounds.Various bacteria
convert the ammonium compounds to nitrate by the fixation of
nitrogen gas into
chemical fertilizer.Much of the nitrogen fertilizer runs off the land and is
added to aquatic ecosystems where nitrogen,like phosphorus,is naturally found
in small quantities.(Nitrogen is a limiting
factor in aquatic
ecosystems.)Humans also alter the nitrogen cycle by burning fossil fuels.High
temperature combustion oxidizes nitrogen gas,producing nitrogen oxides.Nitrogen
oxides include nitrogen dioxide and theprecursors to ozone and acid rain
7.The goods and
services performed by natural ecosystems are essential to human survival.What
is their overallvalue,and of what significance is it to measure this value?
An ecosystem ’s value is
determined by the goods and services performed which are essential to
humansurvival.The goods include lumber,fiber and food.The services include
clean water and air,soil formation,nutrient cycling and waste assimilation.The
overall value of the goods and services provided by ecosystem wasestimate to be
at least $33 trillion.
The reason to measure
the value of ecosystems is to help people make decisions about the
environment.Ifthe value of a wetland is not known we might eliminate the
wetland thinking that the filled land is morevaluable.“We need to give the
natural capital stock adequate weight in public policy decisions
involvingchanges to them.Because these (goods and)services are outside the
market and uncertain,they are too often ignored or undervalued,and the net
result is human changes to natural systems whose social costs far outweightheir
benefits.”
1.Population
growth is the result of a balance between biotic potential and environmental
resistance.What dothese terms mean,and what are the basic patterns of growth of
natural populations?
Biotic Potential is “the number of
offspring (live births,eggs laid,or seeds or spores set in plants)that aspecies
may produce under ideal conditions.” A species ’ biotic potential remains
constant..EnvironmentalResistance
is
“(t)he combination of all the abiotic and biotic factors that may limit
population increase.
Environmental resistance
may increase or decrease depending upon population size.”
The biotic potential of
a species causes the population size to increase.While the population size
isrelatively small,the environmental resistance is low and the rate of
population growth increases.As populationsize increases,the environmental
resistance increases and the rate of population growth declines.Thepopulation
size of some species remains relatively level with moderate increase and
decreases in population
size.Other species have
more dramatic fluctuations in population size.
2.Density-dependent
mechanisms help to regulate natural populations.Explain density-dependence and
density-independence,and apply the concept of critical number.
Density-dependent factors are those
environmental resistance factors that,as they increase,cause anincrease in
“mortality,(such)that population growth ceases or declines.” When population
size decreases theenvironmental resistance factors decrease,letting the
population grow again.Density-independent
factors
are those that cause mortality irrespective of the population density.The population
size can be small or large and
the factor will have the
same effect,e.g.,a sudden,hard freeze will kill plants,seeds or animals
irrespective of the population size.
When a population drops
below a certain minimum size – the critical number – the survival of the
species is unlikely.Density-dependent factors are not typically the factors
that will lower the population size to the
critical number.Long
before the critical number is reached,density-dependent factors have stopped
affecting population size.Density-independent factors,e.g.,habitat
destruction,are usually responsible for bring a population close to or below
the critical number.
3.Predators,parasites
and gazers are important in controlling populations.Explain how they can
operate in a density-dependent manner.
If the population size
of the prey,host,or plant increases,the opportunities for predators,parasites
and grazers increase;there is more food.As more food opportunities arise,the
population size of the predator, parasite or grazer increases.As the number of
predators,parasites,or grazers increase,the number of prey,hosts,or plants will
decrease because fewer of the prey,hosts,and plants will survive to reproduce.
4.Competition
between species can be an important check on populations.How is competition
between plant species minimized by different adaptations and balanced
herbivory?
“Adaptations of a
species to specific conditions enalbes it to thrive and overcome its
competitors in one location but not another.” “A second factor affecting the
competition between plant species is the fact that a single species generally
cannot utilize all of the resources in a given area.Therefore,any resources
that remain may be gathered by other species having different adaptations.”
“Another option is a form of mutualistic
symbiosis.For example,in
warm,humid climates,the branches of trees are often covered with epiphytes,or
air plants.Such plants are not parasitic.There is some evidence that the
epiphytes help to gather the minute amounts of nutrients that come with
rainfall and make them accessible to the tree on which the epiphytes are
located.” “A third and very important factor in multiple-plant balance if
called balanced herbivory.It is easiest
to understand if we
start from the point of view of monoculture – the growth of a single species
over a wide area,a preactice commonly followed in agriculture and forestry
economic efficiency.” “…(V)isualize a monoculture developing in a natural
situation.Its being largely wiped out by an outbreak of its host-specific pest
or herbivore would leave space that might be invaded by another plant
species,which in turn might be
largely wiped out by an
outbreak of its pest,leaving space that might be occupied by a third plant
species and so on.The end result of this process would be a diversified
community,with each species held down in density by its specific
herbivore(s)and the herbivores held in check by their natural enemies.”
5.The
introduction of a foreign species frequently has disruptive ecological
results.Explain why this is the case.
An introduced species
typically does not have predators,parasites,and/or grazers.A non-native plant
may also release chemicals that exclude native species.A non-native species
“may find the environment favorable for survival but it is unlikely that it
fits in the framework of relationships in the new biotic community.“
Examples of exotic
species include rabbits introduced into Australia,chestnut blight,Japanese
beetles,fire ants,gypsy moth,zebra muscle,water hyacinth,kudzu,spotted knapweed
and purple loosestrife introduced into the United States.Rats accompanied
sailors around the world and were introduced into most (if not all)island
ecosystems;most of these
introductions occurred over 100 years ago.Snakes have also been introduced to
many island ecosystems,causing disruptions in bird and other
populations.European grasses were introduced to California (an island
ecosystem)over 100 years ago,nearly eliminating the native bunch
grasses.Pigs,cats
(along with the
automobile,the reason for the endangered status of the Hawaiian Goose),and
mongoose (introduced to control rats but rats are nocturnal and mongoose are
not)are non-native species in Hawaii.
6.Natural
ecosystems may undergo gradual succession until they reach a climax,or more stable
state of ongoing adaptation.What is meant by succession,and what factors are
responsible?
Succession is the
gradual replacement of one community of organisms with another.“Succession
occurs because the physical environment may be gradually modified by the growth
of the biotic community itself,such that the area becomes more favorable to
another group of species and less favorable to the present occupants.”
7.Fire is a major
form of disturbance to terrestrial ecosystems.Of what significance are disturbances,and
what role can they play in maintaining high levels of biodiversity?
Disturbances,e.g.,fire,tornadoes,and
hurricanes,can remove plants and animals from an area,returning the area to an
earlier stage of succession.Fire can increase the quantity of light reaching
the forest flow by reducing the density of the canopy.Fire can also be
necessary the reproduction of some trees,e.g.,the fire pines – knobcone,,bishop
and Monterey -do not release its seed without fire and the seeds need to
germinate on
bare soil.Patchiness
results from having different areas of an ecosystem in different successional
stages.
“Disturbances remove
organisms,reduce populations,and create opportunities for other species to
colonize.”
Because each
successional stage has a different array of species,a mosaic of successional
stages creates in an ecosystem with more species present;biodiversity is
enhanced by a mosaic ecosystem structure.
8.Although
ecosystems are dynamic and viewed as nonequilibrium systems,they may still
function normally even
when
disturbed.What is meant by ecosystem resilience?
“Disturbance and
shifting biotic relationships not only may have little detrimental effect on an
ecoysstem, but may actually contribute to its ongoing function.Ecologists have
referred to this condition as resilience;a resilient ecosystem is one that
maintains its normal functioning – its integrity – even though a disturbance …”
has occurred.
9.What is adaptive
ecosystem management and what are some of its features?
Adaptive ecosystem
management is a management system that accepts the uncertainties in the natural
world.The “…practices
and policies should be seen as tentative and experimental,with a readiness to
changed in the face of necessity.This is especially important in light of our
understanding that wherever human intervene,changes will occur;in addition,as
time goes on,surprises will be inevitable,and new uncertainties
will
appear.
Chapter
5
1.We have already
identified resilience and biodiversity as two important properties of ecosystems
essential totheir sustainability.How have these properties come into existence?
These properties came
into existence over time – “species are gradually ‘molded ’ to cope with other
members of the biotic community and with the abiotic environment.” Species that
are remarkably adapted to the factors of the ecosystem in which they exist have
changed as the environment around them has changed.
We see in the fossil
record tremendous changes in species over time.New species have arisen and
other species have disappeared.A species may,when conditions change,adapt.A
species ability to change when conditions change depends upon the gene pool of
the species.
2.The
characteristics of a population can be modified by differential
reproduction.Give an example of this in terms of selective breeding;in terms of
natural selection.
Differential
reproduction is the ability of some individuals to produce more offspring that
reach reproductive age than other individuals.
In selective
breeding,humans decide on a trait or traits they would like to see in a
species,e.g.,a dog that is tall,thin and has short hair.Breeders then look for
these characteristics in existing dogs and mate these dogs.
Offspring who exhibit
the desired characteristics even more than the parents are mated.With time the
dogs become taller,thinner and have shorter hair.This selection process created
the Great Dane.
In natural
selection,environmental resistance factors determine the individuals who will
successfully produce offspring who will mate.(Discussed in Chapter 4.)These
environmental resistance factors are called selective pressures.Darwin ’s
finches and any of the 500 species of fruit flies that resulted from the
original two
species colonizing the
Hawaiian Islands are examples of natural selection.
Human created
environmental resistance factors have created pesticide and antibiotic
resistance.
3.Mutations and
differential reproduction lead to inevitable changes in the gene pool of a
species.Explain how this occurs.
Mutations provide the
differences among the alleles for a genetic characteristic.Mutations arise
spontaneously or due to exposure to ultraviolet radiation or chemicals.If the
environmental resistance factorsfavor particular characteristics (alleles),then
“(i)ndividuals with any characteristic that provides an advantageover their
cohorts stand a better chance of survival and reproduction.Thus,the alleles for
the beneficialcharacteristic are differentially reproduced,while non-adaptive
alleles are eliminated from the population.”
4.In the face of
environmental changes,some species will survive whereas others will become
extinct.Whatattributes influence the survival of a species?
“Thre are four key
variables among species that will affect whether or not a viable population
ofindividuals is likely to survive new conditions:(1)geographical distribution
(the greater the distribution the
better),(2)specialization
to a given habitat or food supply (the less specialized the better),(3)genetic
variation with the gene pool of the species,and (4)reproductive rate relative
to the rate of environmentalchange (the faster the reproductive rate with
environmental change is fast,the better).”
5.Natural
selection can lead to the development of new species.How does this occur?How is
speciation relatedto biodiversity?
The process is
speciation.As natural selection pressures select from new,randomly generated
and existingmutations,new species are possible.
It is also possible to
obtain two or more species from one.Two prerequisites are necessary for this
tooccur.First,reproductive isolation is necessary.Reproductive isolation is a
result of some physical factorresulting in two or more populations being
isolated from each other such that they are unable to interbreed.Thesecond
necessary factor is that the different sub-populations must be exposed to
different selective pressures.If
the selective pressure
result in sufficiently different characteristics,then the sub-populations will
not be able to interbreed even if they are in contact later.
Speciation is the
creation of new species by “(t)he infusion of new variations from mutations and
the pressures of natural selection serve to adapt a species to the biotic
community and the environment in which it exists or a species “…separates into
smaller populations that do not interbreed with one another.” Both of these
processes increase
biodiversity.“Although it is difficult to imagine,the present array of
plants,animals,and microbes,in all of its diversity,is likely to have
originated through speciation over long periods of time in in every geographic
area on Earth.This,then,is the source of our current biodiversity.”
6.Ecosystems
change over time and vary greatly in different parts of the world,yet ecosystem
resilience is
maintained.Explain
these facts in terms of evolution at the species level.
“(N)atural selection can
modify only preexisting species.(A)land mass will bear species that are
modifications of the species that were there as the land mass was isolated from
other land masses,or that managed to disperse to the isolated land mass.” If
different species exist in similar ecosystems that are remote from each
other,then the material upon which natural selection can work differs.The
organisms occupy the
same niches and habitats
will differ due to the difference in the starting material(species).“Over
time,species…evolve in ways that adapt them to particular abiotic factors (such
as temperature, moisture,and light)and to particular roles in the entire system
as a result of selective pressure brought on by the presence of other
organisms.And these
adaptations to abiotic factors or to other organisms contribute to the
remarkable resilience of ecosystems.
Indeed, such adaptations are the primary source of ecosystem
resilience.”
7.The past
history of Earth has involved the movement of entire continents How does the
theory of plate tectonics explain the movement of continental land masses?
The “Earth ’s crust,
which includes the bottom of oceans as well as the continents,is a relatively
thin layerthat can be visualized as huge slabs of rock floating on an elastic
layer beneath.” “These slabs of rock are called
tectonic plates.”
“Tectonic plates are not stationary.” “The average rate of a plate ’s movement
is about 6centimeters per year.” “Movement of the crust is not gradual,for the plate
boundaries are locked by friction.”
“A boundary may not move
for decades and then snap suddenly in dramatic events.” “The fact that
volcaniceruptions and earthquakes continue to occur is evidence that the
tectonic plates are continuing to move today asthey have over billions of
years.”
8.Evolution is
the most widely accepted explanation for origins,but it is also
controversial.What are the reasonsfor the controversy? “Part of the
controversy over evolution stems from the uncertainties about the mechanisms
that haveproduced the present array of living things.” “Darwin postulated
speciation by gradual changes accumulating
over long periods of
time (but)the fossil record supports the more modern view of punctuated
equilibrium.”
“(T)he DNA of a species
is a capsule view of its evolutionary past,and the base sequences of the DNA
code ofmany groups of species are now yielding new information about the
relationships between closely and moredistantly related species.However,the
farther our explanations reach into the past,the more they are based on
speculation and piecing
together evidence from a variety of sources.”
9.Loss of
biodiversity undercuts the ability of species,ecosystems,and agriculture to
adapt to changingconditions.Why is this the case?
“Biodiversity is really
an expression of the gene pools and the genetic variation within those gene
pools forall the species that inhabit the planet.” ((T)he ability of a species
to adapt to new conditions depends upon … thegenetic variation within its gene
pool.” “As we reduce the size of surviving populations … we inevitablyreduce
the genetic variation within their gene pools and thereby undercut their
potential for future adaptations.”
1.The human
population is undergoing an explosion.When did it start?What are its
causes?What is the current growth rate?
“The population
explosion “…is a recent and unique event – a phenomenon of just the past 100
years..”One could actually argue that it is a phenomenon of the past 150 years
because the human population wasapproximately 1 billion in 1830 and reached 2
billion in 1930;the rapid growth in population probably began
before 1890,“(B)etter
sanitation,medicine,and nutrition brought about spectacular reductions in
mortality,especiallyamong infants and children,while birth rates remained
high.The population was no longer in ‘dynamic balancewith natural enemies –
mainly disease--and other aspects of environmental resistance.”
We currently are in a
trend of declining rate of growth.A growth rate of 1.34 is projected for
1996-2000.
2.The world
comprises high-,middle-,and low-income nations.Identify the nations or
regions,and describerepresentative lifestyles in these three groups.
High income,highly
developed,industrialized countries:Countries included in this group are the
UnitedStates,western Europe,Japan,Australia,New Zealand and Canada.Only 20%of
the world ’s population live inthese countries but these countries control
80%of the world ’s wealth.Middle income,moderately developedcountries:Countries
in this group include Latin America,northern and western Africa,eastern
Asia,eastern
Europe and the countries
of the former USSR.Low income countries:Countries included in this group
areeastern and central Africa,India,and central Asia.Eighty percent of the
world ’s population lives in the middleand low-income countries but these
countries control only 20%of the wealth.
People in the
industrialized countries have access to meat,packaged food,soft drinks,private
cars andmany disposal consumer items.People in middle-income countries tend to
eat grains,do no consume packagedfoods,use bicycles and buses for
transportation and purchase consumer items manufactured for ease of repair.
People in low-income
countries tend to have insufficient quantities of grain for food,drink unclean water,walkfor
transportation and use local biomass for material goods.
3.The most rapid
population growth is occurring in developing countries.What are the social and
environmental consequences of such growth for developing countries?For
developed countries?
Subdivision of farms and
intensification of cultivation have been responses to rapid population growth
indeveloping countries.The result is that “over a billion rural people live in
households that have too little land tomeet even their own meager needs for
food and fuel.” Erosion,,desertification,and decreased food productionhave
resulted. Another response to the rapid population growth in developing
countries has been the opening up of newland for agriculture.This means that
wildlife is eliminated.The goods and services provided by the wild landare
eliminated.The new land put into production is typically notprime agricultural
land,so those who aretrying to farm the land are less than successful.A third
response to rapid population growth in developing countries has been the
emigration of ruralresidents to cities.Life in the countryside is generally
more poverty stricken than life in the city.Access toemployment and social
services is greater in the city.The cities are unable to handle the large
influx of people
and people are forced to
live in areas without sewers or a clean water supply.
Increased participation
in illicit activities is another result of the rapid population growth.If one
cannotgrow enough food or find a job to earn enough money to feed one ’s self
or family,then illicit activities have astrong appeal.The source of many
illicit drugs is the crop grown by the impoverished developing world farmer.
The source of many
exotic and endangered animals and plants is the impoverished individual.The affluentconsumer
who purchases either of the illegal items is part of the chain of
responsibility.
Emigration is a route to
escape the poverty of the developing world.The United States was populated
bypeople escaping poverty.As with the other four responses,this may result in a
personal solution,but it does noteliminate the fundamental problem.Because the
rate of consumption is higher in developed countries,theenvironmental impact
per person is greater with this response than with the other four.
The social consequences
of rapid population growth are increased demands on social
services,increaseddemand for jobs,increased demand for education,and the
like.The particular characteristics of a countrydetermine which of these
demands are the most important.
The environmental
consequences of population growth include increased
erosion,desertification,decreasedfood production,water pollution,and air
pollution.The particular environmental consequences experienced bya country are
determined by their economic development and decisions made by individual
citizens.
4.Population
profiles give the age structure of populations.How are these profiles used to
project futurepopulation?
A population profile
provides information on the proportion of people in each age group.Because age
isrelated to the probability of reproduction,knowing how many people are within
reproductive age and when andhow many people will be reaching reproductive age
is very important for calculating future population size.Predictions of
population size can be made because accurate estimates of birth rates and death
rates are possible.
5.The population
profiles for developed and developing countries are fundamentally
different.What are thedifferences?
The population profile
for a developed country tends to be fairly columnar. The number of individuals
inany particular age group is neither smaller nor larger than the number of
individuals in any other age group. Insome developed countries the number of
individuals in the younger age groups is less than the number o findividuals in
the older age groups.
The population profile
for a developing country tends to be pyramidal. The number of individuals in
the youngest age groups exceeds,by a large margin,the number of individuals in
the oldest age groups.This is partly due to the low life expectancy in the
developing countries (fewer people survive to old age,65+)and
partly due to the large
number of children born per women.
6.Populations in
the developed countries have experienced great reduction in birth and death
rates over time.What is the demographic transition,and what are the different
phases of this transition??
“The basic premise of
the demographic transition is that there is a causal link between modernization
and a decline in birth and death rates.” There are four phases of the
demographic transition,,as seen in the developed world.Phase I is a stable
population size due to high death rates and high birth rates.In Phase II,the
crude death rate drops but crude birth rates remain unchanged,resulting in increased
population size.When a drop in
crude birth rates
begins,due to a drop in fertility rate,Phase III of the demographic transition
has been reached.
The population size is
still increasing in Phase III.Phase IV occurs when the number of births equals thenumber
of deaths and there is no growth in population size.
7.How do the
population profiles,fertility rates,and population projection of developed
countries differ from those of developing countries?How might future population
goals of developed and developing countries contrast?
The population profile
of a developed country tends to be columnar while the profile of a developing
country tends to be pyramid shaped.The fertility rate of a developed country
tends to be at or below replacement while a developing country will have a
fertility rate above replacement.The population projections
of a developed country
will tend to be declining or level while the population growth of a developing
country may have a very short doubling time.
8.What is meant by
population momentum,and what is its cause?
Population momentum
occurs when the population continues to grow for many years “even after the
total fertility rate has been reduced to replacement level.” The cause of
population momentum is that “a small portion of the population is in the upper
age groups,where most deaths occur,and many children are enterring their
reproductive years.” There are more people in ((or soon will be in)the age
group that has babies and few people in the age group that tends to die.Until
the number of people born equals the number of people who die,there will be
population growth
9.Define the crude
birthrate (CBR)and crude death rate (CDR).Describe how these rates are used to
calculatethe percent rate of growth and the doubling time of a population?
The crude birth rate and
death rates are “the number of births or deaths per 1000 of the population
peryear.” “Subtracting CDR from the CBR give the increase (or decrease)per
1,000 per year.Dividing this resultby 10 then puts it in terms of “per 100 ”,or
percent.This is the percent rate of growth.“The doubling time,or the number of
years it will take a population growing at a constant percent per year to
double,is calculated by
dividing the percentage
rate of growth into 70.”
10.What is meant
by the demographic transition.Relate the epidemiologic transition and the
fertility transition,two elements of the demographic transition,to its four
phases.
The “…gradual shift in
birth and death rates from the primitive to the modern condition in theindustrialized
societies is called demographic transition.The basic premise of demographic
transition is thatthere is a causal link between modernization and a decline in
birth and death rates.” The epidemilogic transitionis the “pattern of change in
mortality factors ” that has been observed since the mid--19 th century in developed
nations.The fertility
transition is the change in crude birth rate that has been seen.Phase I of the
demographictransition has high birth and death rates.“Phase II is marked by a
declining CDR – the epidemiologictransition.Because fertility and,hence,the CBR
remain high during Phase II,this is a phase of acceleratingpopulation
growth.Phase III is a phase of declining CBR resulting from a declining
fertility rate;population
growth is still
significant.Finally,Phase IV is reached,in which modern stability is achieved
by continuing lowCDR,but an equally low CBR.
11.How do developed
and developing nations differ regarding their current positions in the
demographic
transition?
The developed nations
are considered to be in Phase IV while the developing nations are in Phase II
or III.
1.What have been
the two basic school of thought regarding population growth?
The first school of
thought is that “We need to concentrate on population policies and
family-planningtechnologies to bring down birthrates.” The second school of
thought is that “If we concentrate ondevelopment,population growth will slow
down ‘automatically ’,as it did in the developed countries.”
2.Discuss the six
specific factors that influence the number of children a couple desires.
Security in one ’s
old age :In
many countries the only means the elder have to support themselves are
theirchildren.Only in developed countries with social security,welfare,retirement
plans and nursing homes is it notthe norm to see parents supported by their
children.Infant
and childhood mortality :High infant mortality
rate is associated with
high birth rate.If you expect that a number of your children will die,you
expect to havea larger number of children.Helping hands:In a developing
country,children are economic assets.At a veryyoung age they begin to
contribute to the family ’s financial well being.In a developed
country,children are an
economic liability.It is
not until the children reach adulthood or beyond that they become
economicallyindependent.Importance of education :If education is seen as
important,a child is more of an economicliability.The longer a child is in
school,the longer it takes for each child to gain economic independence
orcontribute to the family ’s economic well being.When a child is in
school,he/she is not contributing to thefamily income and it costs money to
support the child (food,clothing,shelter,school supplies,etc.)Status of
women :If education is limited
to only men,the decrease in fertility rates is less than if women have
theopportunity to become educated.If for no other reason,being in school
provides a socially acceptablealternative to motherhood.The same can be said
for access to careers.If a woman has socially acceptableoptions other than
motherhood,then a large percentage of women will delay child bearing.The more
years thatelapse between the age at which a child could be conceived and when
the first child is conceived,the fewer
children will be born.Availability of
contraceptives :The
ability to obtain contraceptives when they aredesired will decrease fertility
rates.Studies show that women are interested in increasing the spacing
betweenchildren or limiting the number of children but access to contraceptives
in many countries and in rural areas is
limited.
3.Describe how
poverty environmental degradation and high fertility rates drive one another in
a vicious cycle.
“Increasing population
density leads to a greater depletion of rural community resources like
firewood,water and land,which encourages couples to have more children to help
gather resources and so on.”
4.What has been
the major agency and mechanism for promoting development in poor nations over
the past 45 years?Discuss its past successes and failures.
The World Bank is the
major agency and mechanism for promoting development in poor
nations.Successes:“The gross national products of some countries have increased
as much as fivefold,bringing them from low-to medium-income status,and some
medium-income nations have achieved high income status.’ “Inaddition,great
strides have been made in social progress.” “Literacy rates,the percentage of
the populationwith access to clean drinking water and sanitary sewers,and other
social indicators of development,generally,
speaking,have improved.”
Failures::“a fifth of the world ’s population lives on less than $1 a day,even
morelack access to clean water and sanitary facilities,an estimated 790 million
are malnourished,environmentaldegradation is rampant,and fertility rates remain
high in the poorest countries.Also,the gap between the rich
and poor countries is
growing:The difference between the average income of the riches 20%and the
poorest 20%increased from 30 to 1 in 1960 to 74 to 1 in 1999.” “It is not
accurate either to credit the World Bank forall the progress made or to blame
it for all areas in which progress has been lacking.However,critics point to
many examples wherein
the bank ’s projects have actually exacerbated the cycle of poverty and environmentaldecline.”
5.What is meant
by the debt crisis of the developing world?What is being done in the form of
debt relief to helpresolve this crisis?
“Borrowers become
overwhelmed by interest payments.Theoretically,development projects
wereintended to generate additional revenues that would be sufficient for the
recipient to pay back the loan withinterest.” This did not occur and the “debt
situation continues to be an economic,social,and ecological crisisfor many
developing countries.” “…the concept of fostering the development of poor
countries through massive loans for large-scale projects – whatever the
advantages in enhancing gross national products--has not
broken the cycle of
excess population,poverty,and environmental degradation.”
“The World Bank is
address the problems of poverty more directly through two new
initiatives:theConsultative Group to Assist the Poorest (CGAP)and the Heavily
Indebted Poor Countries (HIPC)initiative.The first of these is designed to
increase access to financial services for very poor households though what
iscalled ‘microfinancing ’.The HIPC initiative addresses the dept problem of 41
of the poorest developing
countries – amounting to
$$207 billion in 1998 – by providing direct debt relief to a level deemed
sustainable .”
6.How has the
World Bank undergone major reform in recent years?
“The Bank now has a
well-organized and influential Environmental Department that provides ‘
intellectualand practical leadership and support in fulfilling the World Bank
’s …environmental and social agenda,’ as the
department ’s mission
statement reads.The Environmental Department has established policies and
proceduresaimed at ensuring that World Bank-financed projects are not
environmentally damaging.The department is
also engaged in helping
developing countries to strengthen their own environmental institutions and
policies.
Most recently,the
Environmental Department has turned its emphasis toward ‘incorporating
environmental andsocial values into the everyday operation of the major sectors
in which the Bank invests,’ according to Director
Robert Watson.”
7.What are the
five interdependent components that must be addressed to bring about social
modernization?
“1.Education –
especially improving literacy and educating girls and women equally with boys
and men..
2.Improving health –
especially lowering infant mortality..3.Making family planning
accessible.4.Enhancingincome through employment opportunities.5.Improving
resource management (reversing environmental
degradation).
8.What are the
key aspects of family planning,and why is family planning of critical
importance to all other aspects of development?
The key aspects include:
a.“Counseling and
education for singles,couples and groups regarding the reproductive
process,thehazards of sexually transmitted disease (AIDS,in particular),and the
benefits and risks of variouscontraceptive techniques.
b.Counseling and
education on achieving the best possible pre-and postnatal health for mother
andchild.The emphasis is on good nutrition,sanitation,and hygiene.
c.Counseling and
education to avoid high-risk pregnancies.Pregnancies that occur when a woman is
too young or too old and pregnancies that follow too closely on a previous
pregnancy are
considered high
risk;they seriously jeopardize the health and even the life of the mother.Any
existing children are also at risk if the mother suffers injury or death.
d.Provision of
contraceptive materials or treatments after people have been properly
instructed about all alternatives.”
“The vigorous promotion
and provision of contraceptives has proved all by itself to have a decided
effect in lowering fertility rates.” “Encouraging and implementing family
planning is the first and most important
step a country can take
to improve its chances to develop economically.”
9.What is meant
by “unmet need ”?
“Women who are not
currently using contraception,but who want to postpone or prevent
childbearing,are said to have an unmet need.”
10.What is
microlending?How does it work?
“As the name
implies,microloans are small – they average just $$67 – and they are short
term,,usually just four to six months.Nevertheless,they provide such basic
things as seed and fertilizer for a peasant farmer to
start growing
tomatoes,some pans for a baker to start baking bread,a supply of yarn for a
weaver,some tools for an automechanic,and so on.” People who have obtained
these loans “…have doubled their incomes in three
years.”
11.How can each
of the following be addressed in a cost-effective way:education;reduction of
infant mortality;
income
enhancement;environmental degradation?
There are no specific
answers to this question.The should use their imaginations to come up with low-
tech,culturally
appropriate ways to address these issues.
12.What was the
significance of the 1994 Cairo conference?What are the agreed-upon strategies
for addressing
the problems of
poverty,excessive population,and environmental degradation?
“The historic
significance of this event is that for the first time in history,the
political,religious,andscientific communities of the world reached a consensus
on the population issue.” The agreed upon strategiesinclude “implementing
strategies for income generation and employment,especially for the rural poor
and those living within or on the edge of fragile ecosystems,” the empowerment
of women through …(e)liminating
gender discrimination
…,(c)hanging customs and laws …,(p)romoting the full involvement of women
incommunity life …,(p)romoting the full involvement of men in family life and
creating policies to ensure men ’sresponsibility to,and financial support
for,their children and families,(a)ssuring the programs are created
andadministered in ways that encourage keeping family members together,(m)aking
access to basic health care andhealth maintenance central strategies for
reducing mortality and morbidity …,(ensuring)complete access to primary school
education for both girls and boys,(a)addressing the root causes of migration
into cities and emigration to other areas,(t)ransferring technology from the
developed countries to the developing countries …,
and (s)etting aside
0.7%of the GNP of each member country of the developed world for the
achievement of the Program of Action ’s objectives throughout the globe.”
1.Certain
properties of soils are described by soil scientists for purposes of
understanding how they were formed.What is a typical soil profile and how can
soil texture be differentiated?
A typical soil profile
consists of the O horizon,consisting of dead organic matter;the A horizon (top
soil),consisting of a mixture of the mineral soil from below with the humus
from above;the E horizon,consisting of a layer from which the minerals have
been leached;the B horizon (subsoil),consisting of the layer to which to
minerals leach from and
A and E horizons;and the C horizon,consisting of the parent mineral material.
Soil texture can be differentiated by the proportion of sand,silt,and clay.If
sand predominates,the soil is called sandy.If silt predominates,then the soil
is called silty.If clay predominates,the soil is called clayey.If
the soil is roughly
40%sand,40%silt,and 20%clay,the soil is called loam.
2.Soils are
classified in a complex taxonomy.What are four common groups of soil important
for agriculture andforestry?
Mollisols,oxisols,alfisols,and
aridisols
3.The soil
environment must provide plants with water,nutrients,and air for the roots.What
are the key attributes of the soil that bear on its being able (or not being
able)to provide these things?
The key attributes of
soil that bear on its ability to provide water,nutrients and air for the roots
are themineral nutrients and nutrient-holding capacity,water and water-holding
capacity,aeration,relative acidity,and
salt level.
4.A dynamic
interaction between mineral particles,detritus,and organisms in the soil is
most important indeveloping the soil ’s key attributes.Describe this dynamic
interaction and how it develops these attributes.
Detritus is the food
source for decomposers and detritus feeders.These organisms consume the
detritus for energy and nutrients and release carbon dioxide,water and minerals
into the soil.The undigested portion of detritus excreted by the soil organisms
is called humus.As minerals go through the guts of detritus feeders,
e.g.,worms,the minerals
adhere to the humus.The clumps of humus create the structure of soil.The soil
structure is the arrangement of soil particles.Humus improves a soil ’s ability
to hold water and nutrients, increases its workability and aeration while
improving the ability of water to infiltrate the soil.
5.Soil
degradation is devastating to the future productivity of a landscape.What are
the major practices leading to erosion and desertification and what are some
ways to combat these harmful processes?
In general,the removal
of plants from soil leads to erosion and desertification.Plant removal can come
in the form of overgrazing,overcultivation and deforestation.Solutions to
overcultivation include no-till agriculture,use of organic fertilizer,contour
strip cropping and shelterbelts.The solution to overgrazing is better land
management.Better management includes fewer grazing animals per acre and the
restoration of
overgrazed lands.The
solution to deforestation is better forest management.Better forest management
includes not removing trees from some areas,harvesting trees at a sustainable
rate,and harvesting other forest products than trees.
6.Certain
irrigation practices may be nonsustainable.Why?Describe the problems that may
develop fromirrigation.
Irrigation in some
locations is not sustainable because the natural level of salt in the water and
soil leads very rapidly to soil salt concentrations that are toxic to
plants.Salinization,“the accumulation of salts in and onthe soil to the point
that plant growth is suppressed ”,can be avoided.If sufficient amounts of water
are applied
to the soil,the salts in
the water will be flushed below the plant root zone.
7.To bring about
better stewardship of soil resources,soil conservation must be promoted at the
level of publicpolicy.Describe some encouraging changes that are taking place
in the U.S.
In 1988 the
U.S.Department of Agriculture started the Low Input Sustainable Agriculture
program,“which provides funding for alternative ” farming methods..Under the
Conservation Reserve Program,passed by Congress in 1985,highly erodible
cropland was allowed to revert to forest or grassland.The development and
implementation of soil conservation programs were required of farmers by the
Food Security Act of 1985 if the
farmer wish to remain
eligible for various government programs.Two new programs were introduced in
1996: the Environmental Quality Incentive Program and the Natural Resources
Conservation Foundation.The former program assists farmers in developing
ecological improvements on the farm.The later program is a non-
governmental
organization working through partnerships “to promote and fund innovative
solutions to conservation problems.”
8.Individual
landholders and herders hold the key to sustainable soil stewardship.What are
some steps beingtaken to promote sustainable agriculture in the developing
world? “They
must be convinced that what they do will work,that it is affordable,and that in
the long run,their ownwellbeing will be improved.Often this requires taking a
number of small,realistic steps.It may also requirehelp in the way of
microlending,sound advice or simply encouragement to experiment.” The UN ’s
Farmer-
Center Agricultural
Resource Management program focuses on “the empowerment of local people,use of
indigenous knowledge blended with modern agricultural science,and (a)strategy
of communicating the results to regional and national levels.”
1.All water on
Earth is constantly recycled,repurified,and reused.How does the hydrologic
cycle inform us on how recycling and repurification occur?
Water rises to the
atmosphere through evaporation or evapotranspiration,condenses into clouds,and
returns to the Earth ’s surface through precipitation.This process purifies
water because only water evaporates.
All impurities are left
behind during the process of evaporation or evapotranspiration.Water will
remain clean
as it returns to the
Earth ’s surface as long as it does not fall through an area with air
pollution.
2.Humans have
three major impacts on the hydrologic cycle.What are they,and what are their
effects?
The three major impacts
humans have on the Earth ’s hydrological cycle are changing the Earth ’s
surface, pollution and water withdrawals.
The effect of changing
the surface of the Earth is to change the water cycle.Little runoff is seen in
an undisturbed ecosystem because most of the water infiltrates into the
soil.Groundwater recharge and quantity of
capillary water in soil
is decreased as less water infiltrates.More water evaporates from the soil when
the quantity of vegetation is reduced.Runoff carries soil to streams,increasing
sedimentation rates. Any water-soluble pollutant can be introduced into the
water cycle.Air pollutants contaminate water during precipitation.Pollutants
are discharged to streams and may be carried with gravitational water to
groundwater.Pollutants,e.g.,pesticides,oil,metals,which are discharged to land
contaminate runoff and may eventually pollute ground or surface waters. Humans
use water in large quantities.If we remove water from surface or groundwater
sources faster than the water is returned by the water cycle,we are altering
the hydrologic cycle.Various consequences result from the mining of water
including land subsidence,saltwater intrusion,loss of riparian habitat,loss of
aquatic habitat,and degradation of estuaries and loss of wetlands.
3.All water must
come from the hydrologic cycle.What are the major uses,points of withdrawal,and
limitationsand consequences of overdrawing water?
The major uses of water
are irrigation,electrical power production,industrial use and residential
use.Themajor points of withdrawal are surface water and groundwater.The major
consequences of overdrawing surface water include water shortages (water is
used at levels seen in wet or ‘normal ’ years,,not dry years)and
ecological effects on
riparian,aquatic,and estuarine ecosystems.The major consequences of overdrawing
ground water include water shortages,land subsidence,diminished levels of
surface water,and saltwater intrusion.
4.Historically,humans
have addressed water problems by obtaining more water.To what degree is this
not a viable option for the future?
People try to obtain
more water by building dams.Dams may adversely impact riparian ecosystem,
increase the risk of disease,eliminate certain types of aquatic habitat,increase
the rate of water evaporation,and displace people.
5.Humans can
reduce their water demands in numerous ways.How can demands be reduced in
agriculture, industry and domestic use?
A number of different
methods have been developed to reduce the amount of water used in agriculture.
Computers are being used to control the flow of water.Drip irrigation systems
deliver water to the base of each plant.Xeroscaping,the planting of drought
tolerant plants,is becoming very important in urban settings.The
1992 National Energy Act
requires the installation of 1.6-gallon toilets.Gray-water recycling systems
are being
installed in some areas.
6.Urbanization
seals surfaces with pavement,increasing stormwater runoff and quickening
concentration times.
Discuss related
problems caused by paving over soil.How should these concepts influence
development?
When soil is covered by
pavement there is virtually no water infiltration.“Even the soil in lawns is
muchmore compacted than in a natural ecosystem and sheds a high percentage of
rainwater.” The water that runs offpaved areas or lawns picks up any substances
present.Oil,metals,pesticides,or fertilizers move with the water
to the surface water.The
contaminants of surface water may move to groundwater.The possibility of
floodingincreases not only from increased amounts of water reaching the stream
but more water reaching the streamsmore quickly.Because the volume of water
reaching streams is greater in paved areas,the probability of
streambank erosion is
increased.When development of an area occurs it is necessary to think about
where precipitation will go.Decreasing
the quantity of paving
and increasing the number of locations where water can be held before reaching
streams(holding ponds)would be useful to decrease the problems caused by
excessive paving.
7.There is
potential for all parties getting together to work out compromises for water
usage between agriculture,cities,and natural ecosystems.What are some policy
options that would encourage this discussion?
The President ’s Council
on Sustainable Development recommended four policy
changes.First,“executiveorders should be issued by the President and state
governors directing federal agencies to promote voluntary,multistakeholder
collaborative approaches toward managing and restoring natural
resources.Second,“public
and private
leaders,community institutions,nongovernmental organizations and individual
citizens should takecollective responsibility for practicing environmental
stewardship.” Third,,“the federal government should play a more active role in
building consensus on difficult issues and identify actions that would allow
stakeholders towork together toward common goals.” Fourth,,“government
agencies,conservation groups,and the private
sector should expand the
use of ecosystem approaches to natural resource management by using
collaborativepartnerships,developing compatible information databases,and
carrying out appropriate incentives for
responsible
stewardship.”
1.In industrialized societies,an agricultural revolution has taken place that has radically affected the practice of farming and its environmental impact.What is industrialized agriculture,how did it develop,and what are its environmental costs?
The agricultural
revolution developed as a result of the industrial revolution.Machinery was
developed that replaced human and animal energy with fossil fuel energy.The
ecological costs of machinery include fossil fuel depletion,air pollution
(including greenhouse gases)and soil compaction.More land was broughtunder
cultivation as traditional agriculture gave way to modern agriculture because
it was possible for one
person to farm more land
as a fossil fuels replaced human and animal energy.Some of the new land brought
under cultivation has been abandoned due to erosion or depletion of water
resources.Any new land brought under production will be at the expense of
forests,wetlands or other wild land.Fertilizer use switched from organic to
inorganic material.Soil fertility has declined due to the loss of humus.The
application rates of
inorganic fertilizers
typically exceed the ability of the soil to hold the fertilizer,resulting in
water pollution. Chemical pesticides provided significant levels of crop
protection but the development of pesticide resistance has decreased the
effectiveness of many classes of pesticide.Pesticides also may harm non-target
species and may adversely affect human health.Irrigation has increased with
modern agriculture.Conflicts over water
resources,salinization,waterlogging,and
groundwater depletion are all possible environmental consequences from
irrigation.High-yielding plant varieties have been developed.While production
increased initially,most of the potential for increasing yield has been
realized.One negative consequence of the high-yield plant
varieties has been a
decrease in the diversity of food crop species.Even within species the
variation in alleles has declined.
2.The
agricultural revolution has been transferred to the developing world in a
process called the Green Revolution.What are the origins and impacts of the
Green Revolution?
The origin of the Green
Revolution is the technology developed in the industrialized world to increase
agricultural productivity.The Green Revolution was dependent on the development
of crop varieties that would produce more food.This lead to selecting plants
that partitioned the energy captured from the sun differently than
normal.Plants with less root material,less vegetative material and more seed
material were chosen for
breeding.This selection
process resulted in the need to increase herbicide use – weeds would compete
more effectively for sunlight.These new plants also had an increase need for
fertilizer and irrigation because the root system was less extensive.
3.In most of the
developing world,agriculture is still practiced in traditional ways,called
subsistence agriculture. How important is subsistence agriculture?
Much of the food grown
and eaten in the developing world comes from subsistence farming.
4.Continued
population growth puts pressure on agricultural practice to keep producing more
food.What are the prospects for increasing food production?
The prospects for
increasing food production are not good.In two areas of the world,Africa and
the former Soviet Union,per capita food production is decreasing.In Africa the
per capita food production has been on the decline since the 1970s because of
increasing population size and lack of modernization. Worldwide per capita
grain production has been declining since 1984.
It is likely that per capita food production will not increase because all the good agricultural land is in production,agricultural land is going out of production due to sali